IE893728L

IE893728L - Polishing plate

Info

Publication number: IE893728L
Application number: IE893728A
Authority: IE
Inventors: Georges Broido
Original assignee: Univ North Carolina
Priority date: 1988-11-22
Filing date: 1989-11-21
Publication date: 1990-05-22
Also published as: EP0370843A1; CA2003381C; FR2639278B1; EP0370843B1; HUT53001A; DK169061B1; DE68902131D1; DK584189A; KR0150779B1; GR3005624T3; JPH02262957A; IE62270B1; US5022191A; CA2003381A1; ES2033542T3; DE68902131T2; HU895835D0; DK584189D0; KR900007550A; ATE78205T1

Abstract

The arcs (3 to 13) cut in the soft parts (1) by a circle of radius equal to approximately half that of the disc and the centre of which is at a distance from that of the disc equal to half the radius of the disc, have a length between 0.5 and 5 mm. Polishing of workpieces. <IMAGE>

Description

62270 -1- 10 15 The present invention relates to circular polishing or lapping plates at the plane surface of which appear flush soft and hard parts, particularly those used in polishing machines comprising a plate driven to rotate about its axis, a work holder offset relative to the plate and driven, particularly by friction, to rotate about its own axis, and an abrasive suspension interposed between the workpieces being polished and the plate, the workpieces being applied against the plate, with the interposition of the suspension, with a certain pressure.

In US-A-3,913,279 a polishing plate is described on whose plane surface appear flush soft parts in the form of islets regularly disseminated in a continuous hard part. In the present specification the expression "hard parts" is used to mean parts harder than the soft parts of the plate. The soft parts are distributed regularly in concentric circles on the plate. No importance is attached to the lengths of the gaps between the hard parts, which in the drawing, and in the corresponding plate on sale commercially, are very large.

In CH-A-641,396 a polishing plate is described in which the soft parts are in the form of a continuous spiral. The width of the spiral is not specified. It is of the order of 10 mm in the corresponding product on sale commercially 2 5 and also has that length in the drawing if it is assumed that the plate illustrated has the diameter usual in the art.

It has now unexpectedly been found that the lengths of the gaps between hard parts play a decisive part in 30 respect of the polishing yield or amount of material removed per unit of time.

The invention therefore relates to a polishing plate giving an increased yield.

The plate according to the invention is 35 characterized in that more than half of the arcs cut in the soft parts by an imaginary circle, whose radius is equal to 9/20ths of that of the disk and whose centre is at a 20 - 2 - distance froa that of the disk equal to half the radius $ of the disk, have a length between 0.5 and 8 mm.

Strictly speaking the curve in question on which the arcs are cut is the trace of the trajectory cm the 5 plate of a point on the workpiece which is to be polished or lapped. Such curves are shown in the drawings. However, for the sake of simplification they may be likened to the imaginary circle with sufficient aoproximation for the purpose of defining the invention. 10 80%, or better still 90%, of the arcs preferably have a length between 0.5 and 5 mm and, even better, between 1 and A mm.

There is an arc length, which is very short compared with the prior art, which gives optimum yield. 15 If, for the purpose of facilitating aanufacture, it is desired to give identical shapes to the hard parts, the criterion laid down by the invention can be met only if the hard parts forms isolated islets in a soft matrix which is continuous, that is to say in a single piece. 20 This form of construction is contrary to the form known in the prior art. It is also found that it enables the plate to be given greater flatness.

The islets are preferably rectangular, the ratio of the length of the longer sides to that of the shorter 25 sides being between 1.5 and 3. The results are improved by depressions formed in the longer sides.

The prior art considered that the optimum yield was achieved with hard parts amounting to 70* and soft parts to 301. However, when the arc length criterion is 30 met, tests show that the best yield is obtained when the hard parts represent from 85 to 952 of the sum of the hard parts and soft parts.

The hard parts of the plate may be powders of cast iron, iron, copper, stainless steel, chromium, carbide, 35 oxides, particularly aluminium oxide, preferably mixed with resins such as polyester resins, acrylic resins and phenolfor aldehyde resins. The soft parts may be metallic powders, for example of copper, bronze, copper and lead alloys, brass, copper and aluminium alloys, aluainiua, lead, antiaony, tin, and zinc, preferably also aixed with resins, particularly polyester, acrylic and phenoIfor ma I-dehyde resins. In these aixtures of resins and aetallic S powders, the resin advantageously represents froa 20 to 40X of the total weight.

The abrasives used are products having on the Mosh scale a hardness of at least 9 and on the Knoop scale a hardness greater than 1,200. These abrasives, which are 10 harder than the hard parts of the plate, are in particular corundum, fused alumina, silicon carbide, boron carbide and diamond, the latter being preferred. The abrasive is in the form of a suspension of the abrasive products mentioned above, in a binder, the particle size of the a b r a -15 sives being between 1 micron and 200 microns, preferably between 10 microns and 40 microns, and the percentage of abrasives in the binder being between 0.2 and 5X by weight and preferably between 1 and 3X by weight. The binder may consist of a mixture of water and glycols, the glycols 20 representing from 10 to 60% of the total weight of the binder and preferably from 20 to 501 of that weight. The binder may also consist of a mixture of water and kerosene, the latter reoresenting from 40 to 60% of the total weight of the binder. 25 In the accompanying drawing, given solely by way of example. Figures 1 to 4 are plan views of plates according to the invention, which have a diameter of 230 mm, and Figure 5 is a graph illustrating the invention. 30 The lapping plate shown in Figure 1 consists of a matrix 1 of a mixture of resin and copper, the resin representing 2/3 by weight of the mixture. The matrix 1 is continuous and constitutes the soft parts. The hard parts consist of islets 2, whose faces flush with the surface of 35 the plate are circular, having a diameter of 25 ma.

The curve C1 is also shown, which is the trace on the polishing plate of a point of an object to be polished. On the soft matrix this curve C1 cuts arcs of which more than 502 have a length between 1 and 5 aa. This curve aay also be likened to the iaaginary circle C whose radius is equal to half that of the disk, and whose centre is at a distance froa that of the disk equal to half the radius of 5 the disk. On the soft aatrix this circle cuts the arcs 3 to 13, whose respective lengths are 8, 3, 6, 12, 2, 17, 10, 7, 8, 6, 2 and 12.

In Figure 2 the islets 22 have substantially the • shape of a rectangle whose longer sides are provided with 10 depressions. The space between two shorter sides 23 of a rectangle is 2 mm. The space between the two depressed parts 24 of the longer sides of the rectangle is likewise 2 mm. The space between the longer side segments immediately adjacent to the shorter sides 23 is 2 um. The 15 space between the portions connecting the depressed parts to the remainder of the longer sides is only 1 mm.

In Figure 3 the hard rectangular islets 32 are disseminated in a matrix 33. The distance separating two islets, measured along their sides, is 2 mm. 20 In Figure 4 the hard islets 42 are disseminated in the soft matrix 41, the distance separating two islets being such that the arcs cut in the soft parts have lengths between 0.5 and 5 mm.

In order to deteraine the yield of the plates, six 25 cylindrical workpieces of a diameter of 20 mm are lapped by applying a pressure of 265 g/cm^ in a lapping machihe, the speed of rotation of the machine being 150 revolutions per ainute and the speed of rotation of the workpiece holder being 175 revolutions per minute, which corresponds 30 to a linear soeed of the workpieces of 0.8 m/s. Six cycles lasting 5 minutes each are carried out. The abrasive used is brand MM 381 diamond liquid supplied by the applicants. The removal of material is measured in microns every five minutes on the six workpieces. The a 35 total removal of material is also measured on all the workpieces in all the cycles.

For a prior art plate of the Applicants, as described in the United States of America patent previously aentioned, the reaoval of Material amounts to 615. This ■*teri«l reaoval value is taken as a base index equal to 100.

The results obtained are shown in Table I. In Table II the soft islets of the prior art plate have been replaced with hard islets in such a tanner that these hard islets represent 71X of the plate surface, whereas the soft islets represented 70X of the prior art plate. The results obtained are shown in Table II.

TABLE I No keaoval of material removal of mterial removal of material removal of material removal of material 1 19 20 20 20 24 2 16 20 20 16 22 3 16 21 17 19 21 4 19 22 19 21 22 S 20 20 25 21 23 6 22 20 22 24 24 total REMOVAL Of MATERIAL 112 123 123 121 136 total removal Of material/5 cycles kan removal of material 3,73 4,1 4,1 4,03 4,53 615 DIVERGENCE 6 6, 8 8 3 - 6 -table II No REMOVAL Of MATERIAL REMOVAL OF MATERIAL REMOVAL OF MATERIAL REMOVAL Of MATERIA! REMOVAL Of MATERIAL I 31 26 31 31 29 2 27 27 28 24 26 3 27 27 28 26 23 4 33 30 26 28 29 5 6 36 34 27 26 32 36 33 26 35 33 total removal of material/5 cycles total removal of material 193 167 178 168 180 836 KAN »EPOvAL OF MATERIAL 6,43 5,56 5,93 5,6 6 smflGlMCE 9 4 11 7 15 The yield is 144.

Table III gives the results for a plate of the 20 same type as that in Figure 1, but having islets of a diameter of 20 mm. The percentage of islets is 70X. The yield is 141. Table IV gives the results for a plate of the same type as that in Figure 1, but with islets of a diameter of 13 mm. The percentage of islets is 72. The 25 yield is 135.

Tables V to X give the results obtained with plates according to Figure 2, but with spaces between the two shorter sides of the hard islets and the depressed parts of the longer sides of the hard islets equal re-30 spectively to 0.5, 1, 2, 4, 6 and 8 mm. The percentages of hard islets are 95, 91, 81, 69, 57 and 51 respectively. The yields are 126, 131, 148, 137, 122, 103. Figure 5 plots the variation of removal of material with respect to the spaces between the hard parts. It can clearly be seen 35 that maximum removal of material is obtained with a value close to 2 mm, the range extending froir 0.5 to 6 mm corresponding to removals of material greater than 750. There is a close correlation between the length of the arcs cut - 7 - in the soft parts and the lengths of the spaces between the hard parts.

In all these tables it has in addition been found that the smaller the difference in measurements (diver-5 gence) between the workpieces for the different passes, the better the yield.

Table XI gives the results obtained with a plate according to Figure 3, and Table XII the results with a plate according to Figure 4. The yields are 147 and 140. 10 TABLE III 15 20 25 No removal of material removal OF material removal OF material REMOVAL OF MATERIAL HMOvfcL OF material 1 27 23 34 32 29 2 24 27 29 30 24 3 22 29 30 24 22 4 28 27 28 26 25 5 6 30 32 33 35 32 32 32 36 31 32 total removal Of mate»ial/5 ctcles TOTAL REMOVAL Of MATERIAL 163 174 185 180 163 865 mean REMOVAL Of MATERIAL 5,43 5,8 6,16 6 5,43 DIVERGENCE 10 8 6 8 10 - 3 - table iv NO removal of material removal of material removal of material removal of material removal of material I 2 2. 26 30 28 31 5 2 20 22 28 28 29 3 21 23 25 27 30 4 23 23 35 26 32 5 3 1 24 34 35 29 10 6 24 28 34 3 6 29 TOTAL REMOVAL Of material/; cycles total REMOVAL Of MATERIAL 141 146 186 180 180 833 15 ME AM REMOVAL OF MATERIAL 4,7 4 , 86 8,2 6 6 divergence 11 6 10 10 3 TABLE V 20 NO REMOVAL OF MATERIAL REMOVAL of MATERIAL REMOVAL OF MATERIAL REMOVAL OF MATERIAL REMOVAL OF MATER J AL 1 22 25 27 29 23 2 23 2 7 23 3 3 24 3 19 27 30 29 24 25 4 21 2 4 3 1 31 24 5 19 26 29 29 23 r 0 22 25 27 28 23 total removal of materials cycles 30 TOTAL REMOVAL OF MATERIAL 1 26 154 177 179 139 775 me am removal of material 4,2 5,13 5,9 5 ,96 4,6 35 divergence 4 3 8 5 1 table vi No REMOVAL Of MATERIAL REMOVAL Of MATERIAL removal or material REMOVAL Of MATERIAL REMOVAL Of MATERIAL 1 2 3 4 t; 6 24 25 24 29 24 24 27 26 28 26 26 24 27 23 29 28 29 25 27 3 1 30 30 27 28 27 25 27 27 26 28 total removal Of material/5 cycles total removal Of material 150 157 169 173 1ST 806 mam fiEJWVAL Of MATERIAL S 5,23 5,63 5 ,76 5,2 divergence 5 5 2 4 3 TABLE VII No REMOVAL or REMOVAL Of REMOVAL Of REMOVAL Of REMOVAL Or MATERIAL MATERIAL MATERIAL MATERIAL MATERIAL 1 23 23 32 31 3° 2 30 30 32 32 31 3 31 31 32 33 31 4 29 30 32 32 23 c 28 29 32 31 29 6 29 28 31 30 29 TOTAL REMOVAL Of MTERIAL/5 CTCLfS TOTAL REMOVAL Of 175 176 191 189 178 909 MATERIAL DIVERGENCE 3 3 1 3 3 - 10 -table viii No REMOVAL Of MTtaiM.

KMNALOf MT1IIAL KNOVM. Of MATERIAL tIMOVAL Of MATERIAL REMOVAL Of MATERIAL 1 26 29 27 22 26 2 26 30 27 30 30 3 28 29 29 30 28 4 29 27 30 30 29 5 27 28 29 27 28 6 25 28 26 29 27 TOTAL REMOVAL OF MATERIAL/S CYCLES TOT AL REMOVAL Of MATE#IAL 16 1 171 168 1 75 168 84 3 MEAN REMOVAL OF MATERIAL 5,36 5,7 5,6 5,83 5,6 divergence 4 4 4 8 4 TABLE IX No REMOVAL Of MATERIAL REMOVAL OF MATERIAL REMOVAL OF MATERIAL REMOVAL OF MATERIAL REMOVAL OF MATERIAL i i 23 26 24 24 24 i 23 27 25 25 25 3 25 27 26 26 27 4 ■« 26 26 25 24 29 C 24 26 24 25 24 6 23 26 24 25 24 TOTAL REMOVAL Of MATERIAL/; CYCLES TOTAL removal Of MATERIAL 144 158 148 149 153 752 mver6ence 3 3 2 2 5 - 11 table x No REMOVAL Of REMOVAL OF tEMOVAL OF removal or REMOVAL Of MATERIAL MTUIM.

MTfRlAL MATERIAL MTU IAL i 20 21 22 21 21 2 22 22 21 20 22 3 22 21 22 21 23 4 19 22 21 20 23 5 21 21 2C 21 20 6 19 22 19 21 22 TOTAL REMOVAL Of MATERIAL/S CTCLES TOTAL 124 9EM0VAL OF 123 12S 125 131 632 MATERIAL BIVER6EMCE 3 1 3 1 3 TABLE XI No REMOVAL Or MATERIAL REMOVAL of MATERIAL removal of material REMOVAL Of MATERIAL REMOVAL OF MATERIAL 1 26 32 30 31 31 2 31 29 30 32 31 3 30 29 31 33 31 4 32 27 33 33 29 S 29 28 31 3 1 28 6 27 31 28 30 29 TOTAL REMOVAL OF MATERIAL/J CTCLES total REMOVAL Of MATERIAL 175 176 183 190 179 903 HVERSOHE 6 5 5 3 3 table xii No tUML or MTtlUL KMVM Of MTUIM.

KMVM. or MTUIM.

KMVM. or RATE*IAL KMVM. or MTUIM 1 27 28 28 30 30 2 28 30 27 33 29 3 28 29 30 33 30 4 28 29 26 33 29 5 29 26 30 30 29 6 CO rv| 26 28 30 29 TOTAL REMOVAL Of IWTEHIAL/S CTCLES TOTAL REMOVAL Of MTtRlAL 168 168 169 189 167 861 DIVERGEMCE 2 4 4 3 1 -13-

Claims

1. Circular polishing plate with a center, at the plane surface of which appear flush soft and hard parts, characterized in that more than half of arcs cut in the soft 5 parts by an imaginary circle, whose radius is equal to 9/20ths of that of the disk and whose center is at a distance from that of the disk equal to half the radius of the disk, have a length between 0.5 and 8 mm.

2. The plate of claim 1, characterized in that at 10 least 80% of the arcs have a length between 0.5 and 5 mm.

3. The plate of claim 2, characterized in that at least 90% of the arcs have a length between 0.5 and 5mm.

4. The plate of claim 1 to 3, characterized in that the length of the arcs is between 1 and 4 mm. 15

5. The plate of anyone of the preceeding claims, characterized in that the hard parts form isolated islets in a soft matrix, which is continous.

6. The plate of claim 5, characterized in that the islets are rectangular, with longer sides and shorter sides, 20 the ratio of the length of the longer sides to that of the shorter sides being between 1.5 and 3.

7. The plate of claims 5 or 6, characterized in that depressions are formed in the longer sides.

8. The plate of claims 1 to 7, characterized in 25 that the hard parts represent from 85 to 95% of the sum of the hard parts and soft parts.

9. A circular polishing plate according to claim 1, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings. F. R. KELLY & CO., AGENTS FOR THE APPLICANTS.